Top dead center
A guy checked mine for me years ago, he had this little "whistler" that he attached to the end of the air hose. Popped the proper fuses (fuel pump and one other I think) so the engine couldn't fire up, then he had me slowly bump the key to turn the engine over little by little. When the whistle sound stopped, that piston was at TDC. Then he took the whistler off and attached the air hose and did the test on that cylinder.
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it depends on the engine with an lt1 its probably easier to just pull a valve cover and watch the action of the rockers as your turning it over, not as easy with a ls1 because of the coils in way
you didn't say how exact your trying to be either i guess if your just trying to get the valves closed so you can do a leak down test.... so who knows....
you didn't say how exact your trying to be either i guess if your just trying to get the valves closed so you can do a leak down test.... so who knows....
